I think for Lemons purposes there's nothing wrong with going into your search agnostic and making your decision based on what you then have to work with.
That is how we ended up racing a Beetle, which isn't exactly the first car to spring to mind when you think about going racing. We stumbled across a New Beetle with 5 spd manual and the 1.8 turbo motor, sun-rotted plastic and a very mildewed interior (any VWs with sunroofs that live outdoors will be leaky & mildewed), but moderately low miles and running well, and the price was right. Since it shares driveline and suspension with the Mk IV Golf and Jetta, parts are easy to find and not too expensive. Just happened to overhear someone saying "We're selling my wife's Beetle. The book value was only $1100-$1200, but with the interior in the shape it is in, we probably won't get $500 for it". I asked a few questions and offered $350 cash. So look around and be flexible if you're not hung up on something specific. Also keep an eye on the Lemons forums and on the Facebook pages (Unofficial Lemons page, Citrus Racing Lounge, etc.) for teams selling cars - it is a good bit cheaper to buy a car than to build your own.
The bottom line is that you can have a ball flogging anything around a racetrack. If you aren't wrapped up in trying to win, just find something in decent mechanical shape that is easy to work on (we missed that part - Beetles are a little snug under the hood). Fix it up, make it reliable, and have fun!
